1. Field of the Invention
The present invention relates to a method of forming a light-emitting element, specifically a method of forming a light-emitting element by separating an active layer at a separation layer to form the active layer on a substrate.
2. Description of the Related Art
Some technologies for transferring an active layer onto a supporting substrate by bonding a substrate having a separation layer and an active layer onto the supporting substrate and then separating the bonded substrate at the separation layer have been disclosed by, for example, Japanese Patent Application Laid-Open No. 2004-146537.
In the above described technologies, however, the bonded substrates are separated by etching the separation layer. Accordingly, when the substrates having a size of a substrate scale (normally, 2 inches Φ or larger) are separated from each other, it takes an extremely long period of time to separate the substrates by a method of etching the separation layer mainly from side faces of the substrates. For this reason, there is no example which has been industrially commercialized.
For this reason, some methods for the purpose of downsizing a region to be etched are proposed, which an active layer is patterned into necessary (island-shaped) regions, the regions are bonded onto a supporting substrate, and then a separation layer is etched to separate the regions from an original substrate, and which are disclosed by, for example, Japanese Patent Application Laid-Open Nos. 2002-299589, 2001-156400, 2002-15965, 2001-36139, and 2005-12034.
One of the reasons why the active layer is separated by using substrates of a substrate scale in the conventional technologies as described above is to reuse (recycle) an expensive substrate, which is an important view point.
Specifically, the technology includes recycling the substrate by repeating the steps of: separating a substrate from a separation layer to return the substrate into an original condition; subjecting the substrate to a cleaning step and the like; and then growing a separation layer and an active layer again on the substrate.
In actual fact, however, the technology has a disadvantage that when the films are repeatedly grown thereon at a high temperature, the substrate becomes very brittle because distortion is accumulated in the substrate due to heat, and has been technically difficult.
In addition, the technology has lost one half its initial effectiveness of recycling because a cost of epitaxial growth is high as well as a substrate cost.